To determine the extent to which Acciona SA should utilize hybrid bonds, we must analyze the company's current capital structure, the cost of capital environment, and the specific constraints provided by S&P Global Ratings regarding equity credit for hybrids.

**1. Analysis of Capital Structure (2022 Data)**

First, we calculate the relevant components of the capital structure based on the provided annual report facts for the period ending 2023-01-01 (representing the 2022 fiscal year end).

*   **Equity:** The total Equity is reported as **6,304,000,000 EUR**. This includes Equity Attributable To Owners Of Parent (4,885,000,000 EUR) and Noncontrolling Interests (1,419,000,000 EUR).
*   **Debt:** We need to identify interest-bearing debt.
    *   Noncurrent Financial Liabilities:
        *   Participaciones Preferentes Obligaciones YOtros Valores Negociables No Corrientes: 3,101,000,000 EUR
        *   Noncurrent Portion Of Noncurrent Loans Received: 2,624,000,000 EUR
        *   Noncurrent Lease Liabilities: 439,000,000 EUR
        *   *Note: Deferred Tax Liabilities, Provisions, and Other Noncurrent Liabilities are typically excluded from "Debt" in leverage ratios unless specified otherwise, but "Total Adjusted Capital" usually refers to Debt + Equity. Let's look at standard definitions. S&P's "Total Adjusted Capital" is generally Debt + Equity. Here, "Debt" usually includes bank loans, bonds, and lease liabilities. The line item "Participaciones Preferentes..." likely contains existing hybrid instruments or senior debt. Given the name "Obligaciones" (Bonds), these are likely senior unsecured bonds. Let's assume for the baseline calculation that current debt consists of Loans and Bonds.*
    *   Current Financial Liabilities:
        *   Participaciones Preferentes Obligaciones YOtros Valores Negociables Corrientes: 1,139,000,000 EUR
        *   Current Loans Received And Current Portion Of Noncurrent Loans Received: 553,000,000 EUR
        *   Current Lease Liabilities: 72,000,000 EUR

    Let's sum the clear interest-bearing debt (Loans + Bonds/Notes + Leases):
    *   Noncurrent Debt = 3,101 + 2,624 + 439 = 6,164 million EUR
    *   Current Debt = 1,139 + 553 + 72 = 1,764 million EUR
    *   **Total Debt** ≈ 7,928 million EUR.

    *Alternative Interpretation:* Sometimes "Participaciones Preferentes" refers to preferred shares which might be equity or hybrid. However, they are listed under Liabilities in the breakdown (Noncurrent Liabilities and Current Liabilities sections), suggesting they are treated as debt or mandatory redeemable instruments in this specific reporting format, or simply bonds ("Obligaciones"). Let's assume Total Debt is approx **7,928 million EUR**.

*   **Total Adjusted Capital:**
    *   Total Adjusted Capital = Total Debt + Total Equity
    *   Total Adjusted Capital = 7,928 + 6,304 = **14,232 million EUR**.

**2. S&P Global Ratings Constraint Analysis**

S&P Global Ratings limits the equity credit on hybrids to a maximum of **15% of total adjusted capital**.
*   Max Equity Credit Allowed = 15% * 14,232 million EUR = **2,134.8 million EUR**.

Hybrid bonds typically receive 50% equity credit from rating agencies like S&P (depending on the specific terms, deferrability, etc.). If we assume a standard 50% equity credit for hybrid bonds:
*   Let $H$ be the amount of Hybrid Bonds issued.
*   Equity Credit = $0.50 \times H$.
*   Constraint: $0.50 \times H \le 2,134.8$ million EUR.
*   Max Hybrids ($H$) = $2,134.8 / 0.50$ = **4,269.6 million EUR**.

This represents the *maximum* amount of hybrids the company *could* issue before hitting the cap where additional hybrids would no longer receive equity credit (and thus would be treated purely as debt, increasing leverage ratios without benefiting equity ratios).

**3. Strategic Assessment: To what extent *should* they utilize?**

The question asks for the extent of utilization relative to the cap. The options are 0%, 25%, 50%, 75%, 100%.

*   **Market Environment (2022):** The swap curves and bond spreads show a significant increase in interest rates in 2022 compared to 2020-2021.
    *   10Y Swap Average went from -0.143% (2020) to 1.927% (2022).
    *   iShares Core Euro Corp Bond yield went from 1.171% (2020) to 1.085% (2022) - *Wait, the average dropped slightly but the bear case is higher*. Actually, looking at the Sub-Sen Delta for IBOXX EUR Non-Financial IG, the spread/yield metric increased from 1.298 (2021) to 2.295 (2022). This indicates a **more expensive cost of debt** environment.
*   **Cost of Hybrids vs. Equity:** Hybrids are generally cheaper than pure equity (dividends are often tax-deductible or deferred, and investors accept lower yields than equity shareholders due to seniority). However, they are more expensive than senior secured debt.
*   **Current Leverage:**
    *   Debt/Equity Ratio = 7,928 / 6,304 ≈ 1.26x.
    *   Debt / (Debt + Equity) = 7,928 / 14,232 ≈ 55.7%.
    *   This is a moderate leverage level for an infrastructure/construction company like Acciona.

*   **Utilization Logic:**
    *   Issuing hybrids up to the cap (100% utilization) maximizes the "equity cushion" recognized by rating agencies, potentially supporting a higher credit rating or allowing for more senior debt issuance while maintaining leverage targets.
    *   However, issuing hybrids is costly. In a rising rate environment (2022), the coupon on new hybrids would be high.
    *   Does the company *need* to optimize its rating via hybrids? Acciona is an investment-grade company. Maintaining a strong balance sheet is key.
    *   Usually, companies do not fill the hybrid bucket to 100% unless they are aggressively leveraging or have a specific strategic need to de-lever the *reported* equity ratio without issuing actual equity.
    *   Looking at the "Participaciones Preferentes" line items (3,101 + 1,139 = 4,240 million EUR), it is highly probable that Acciona **already has** a significant amount of hybrid-like or preferred instruments outstanding. If these are already counted as debt in our "Total Debt" figure but might be candidates for reclassification or if they are the existing hybrids, we need to see how much "room" is left.
    *   If the existing "Participaciones Preferentes" (4,240m) are treated as debt for the ratio but are structurally hybrids, they might already be consuming the equity credit capacity.
    *   Let's check the magnitude. The max hybrid capacity we calculated was ~4,270 million EUR. The existing "Participaciones Preferentes" are ~4,240 million EUR. This is a near-perfect match.
    *   This suggests that Acciona has **already utilized** almost the entire capacity allowed by the S&P cap for instruments that could qualify for equity credit.
    *   Therefore, the question "To what extent *should* this company utilize hybrid bonds relative to the cap?" implies looking at the *target* utilization. Since they are already at the limit (4,240m existing vs 4,270m max), they are effectively at **100%** utilization of the beneficial capacity. Issuing more would not yield equity credit and would just add expensive debt. Issuing less would mean redeeming existing hybrids, which might not be optimal if they want to maintain the equity credit buffer.
    *   However, often "utilize relative to cap" questions in this format refer to a *target* policy. Many investment-grade corporates target a partial utilization (e.g., 50% or 75%) to retain flexibility. But given the data shows existing instruments matching the cap, the *current* state is 100%.
    *   Let's re-read carefully: "To what extent *should* this company utilize...". This is a prescriptive question.
    *   If the company already has ~4.24bn in these instruments, and the cap allows ~4.27bn, they are maxed out.
    *   Is it *optimal* to be maxed out? In a high-rate environment, hybrids are expensive. But if they are already issued, the decision is whether to issue *more* or redeem. The question likely asks for the optimal *target* level of hybrid capital in the structure.
    *   Standard corporate finance theory for IG companies often suggests using hybrids to optimize the WACC and rating. A common "best practice" or observed behavior for companies optimizing their rating under S&P rules is to fill the bucket to the extent it supports the desired rating without over-levering.
    *   However, there is a nuance. If the "Participaciones Preferentes" are *already* hybrids, the company is at 100% utilization. If the question implies "what is the recommended utilization level for a company like this", and we see they are *at* the cap, it suggests their strategy *is* 100%.
    *   Let's consider the options. 0% is wrong (they have them). 25% is too low given their existing base. 50% is possible if they are over-levered, but their leverage is moderate. 100% implies maximizing the equity credit benefit.
    *   Given the precise match between the calculated cap (~4.27bn) and the existing "Participaciones Preferentes" (~4.24bn), it is evident that the company's capital structure is designed to **fully utilize** the equity credit allowance provided by S&P. This maximizes the leverage capacity while maintaining the investment grade rating metrics.

Therefore, the company is utilizing (and should continue to utilize, to maintain this optimized structure) the full extent of the cap.

<answer>100%</answer>